TRAPPIST-1, also designated as 2MASS J23062928-0502285, is an ultra-cool dwarf star that is slightly larger, but much more massive than the planet Jupiter, located 39.5 ly (12.1 pc) from the Sun in the constellation Aquarius. As of February 2017, the dwarf star has been shown to host seven temperate terrestrial planets, a larger number than detected in any other planetary system.

A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. The technical name is the perigee-syzygy of the Earth–Moon–Sun system. The term supermoon is not astronomical, but originated in modern astrology. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events such as earthquakes and volcanic eruptions, but there is no evidence of such a link.

The opposite phenomenon, an apogee-syzygy, has been called a micromoon, though this term is not as widespread as supermoon.

The most recent supermoon occurred on November 14, 2016. This was the closest supermoon since January 26, 1948, and will not be surpassed until November 25, 2034 The closest supermoon of the century will occur on December 6, 2052. The next supermoon will be on December 14, 2016.

Occasionally, a supermoon coincides with a total lunar eclipse. The most recent occurrence of this was in September 2015, while the next time will be in October 2033.

The Andromeda Galaxy (/ænˈdrɒmᵻdə/), also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth. It is the nearest major galaxy to the Milky Way and was often referred to as the Great Andromeda Nebula in older texts. It received its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda.

Being approximately 220,000 light years across, it is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies. Despite earlier findings that suggested that the Milky Way contains more dark matter and could be the largest in the grouping, the 2006 observations by the Spitzer Space Telescope revealed that Andromeda contains one trillion (1012) stars: at least twice the number of stars in the Milky Way, which is estimated to be 200–400 billion.

The first direct gravitational wave observation was made on 14 September 2015 and was announced by the LIGO and Virgo interferometer collaborations on 11 February 2016. The waveform, detected by both LIGO observatories, matched the predictions of general relativity for a gravitational wave emanating from the inward spiral and merger of a pair of black holes and subsequent “ringdown” of the single resulting black hole. The signal was named GW150914 (i.e., “Gravitational Wave 2015–09–14“). This was also the first observation of a binary black hole merger, demonstrating the existence of binary stellar-mass black hole systems, and that such mergers could occur within the current age of the universe.

This first observation was reported around the world as a remarkable accomplishment for many reasons. Efforts to prove the existence of such waves had been ongoing for over fifty years, and the waves are so minuscule that Einstein doubted they could ever be detected. The waves given off by the cataclysmic merger of GW150914 reached Earth as a ripple in space-time that changed the length of a 4-km LIGO arm by a tiny fraction of the width of a proton, proportionally equivalent to changing the distance to the nearest star by one hair’s width. The energy released during the brief climax of the event was immense, with about three solar masses converted to gravitational waves and radiated away at a peak rate of about 3.6×1049 watts — more than the combined power of all light radiated by all the stars in the observable universe. The observation was also heralded as confirming the last remaining unproven prediction of general relativity, and validating its predictions of space-time distortion in the context of large scale cosmic events, as well as inaugurating a new era of gravitational-wave astronomy, allowing probing of violent astrophysical events unobservable until now.